Texas Instruments SN74F657DWRE4

Overview

SN74F657DWRE4 from Texas Instruments is an octal transceiver with integrated 8-bit parity generator/checker and 3-state outputs, designed for bidirectional bus interfacing in TTL-level systems. It supports A↔B data flow direction control via T/R input, provides 64 mA sink capability at B-port outputs, and operates across 4.5–5.5 V supply at 0°C to 70°C. Used in legacy industrial backplanes and memory expansion interfaces requiring error-detectable data transfer.

For engineers reviewing the SN74F657DWRE4 datasheet, SN74F657DWRE4 pinout, SN74F657DWRE4 application, or SN74F657DWRE4 equivalent, key selection criteria include its dual-mode parity handling (ODD/EVEN-selectable), ERR output behavior during receive mode, 3-state enable timing (tPZH/tPLZ ≤ 9 ns), and SOIC-24 package compatibility with legacy board layouts.

Technical Context

The SN74F657DWRE4 implements a synchronous bidirectional transceiver architecture where T/R controls signal direction and OE enables/disables both A and B ports into high-impedance states. Its parity logic evaluates all eight A or B inputs simultaneously to generate or verify even/odd parity on the PARITY pin.

In transmit mode (T/R = HIGH), PARITY is an output reflecting the parity of A-port bits; in receive mode (T/R = LOW), PARITY becomes an input while ERR asserts HIGH only when received parity matches expected parity (e.g., ODD/EVEN = LOW + even number of HIGHs on B port → ERR = HIGH).

Key Specifications

Pinout & Package

SN74F657DWRE4 is housed in a 24-pin SOIC (DW) package with 300-mil width, RoHS-compliant NiPdAu lead finish, and moisture sensitivity level 1 (260°C peak reflow). Pin numbering follows standard top-view orientation with Pin 1 at bottom-left corner.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal transceiver-with-parity applications.

Compared with SN74F657DWRE4, SN74F657N offers identical functionality in PDIP format for breadboarding or field repair, while SN74LS657N trades speed and drive for lower static/dynamic power - making it viable only where timing slack permits.

Availability

SN74F657DWRE4 is available at Aetrix Electronics and suitable for memory expansion interfaces, industrial backplane buses, legacy computer system upgrades, and test equipment data capture requiring stable component supply and long-term obsolescence support.

Supply support for SN74F657DWRE4 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74F657DWRE4 belongs to TI's 74F family of fast TTL logic devices, engineered for high-speed, low-noise bus interfacing in commercial-temperature computing and control systems.

FAQ

What is the function of the ODD/EVEN pin on the SN74F657DWRE4?

The ODD/EVEN pin on the SN74F657DWRE4 selects the parity scheme used by the internal generator/checker circuit. When set LOW, the device operates in even-parity mode; when HIGH, it uses odd-parity mode. This setting determines whether the PARITY output reflects an even or odd count of HIGH bits on the active port during transmit mode, and governs the expected parity value during receive mode validation - directly affecting ERR output behavior in SN74F657DWRE4 systems.

How does the ERR output behave during receive mode in the SN74F657DWRE4?

In receive mode (T/R = LOW), the ERR output of the SN74F657DWRE4 goes HIGH only when the number of HIGH bits on the B port matches the expected parity defined by the ODD/EVEN setting and the PARITY input. For example, with ODD/EVEN = LOW (even parity) and an even number of HIGHs on B1–B8, ERR = HIGH indicates correct parity; any mismatch results in ERR = LOW. This real-time hardware validation occurs without software intervention and is intrinsic to SN74F657DWRE4's architecture.

What is the maximum sink current supported by the B-port outputs of the SN74F657DWRE4?

The B-port outputs of the SN74F657DWRE4 support a maximum sink current (IOL) of 64 mA per pin under recommended operating conditions (VCC = 4.5 V, TA = 0°C to 70°C). This rating allows direct interfacing with multiple TTL inputs or moderate capacitive loads on shared buses, and is confirmed in the "Recommended Operating Conditions" table of the SN74F657DWRE4 datasheet - distinguishing it from weaker alternatives like SN74LS657N.

Can the SN74F657DWRE4 be used in place of separate SN74F245 and SN74F280B ICs?

Yes - the SN74F657DWRE4 integrates the core functions of both SN74F245 (octal transceiver) and SN74F280B (8-bit parity generator/checker) into a single SOIC-24 package with identical pin assignments for A/B ports and shared control signals. This consolidation eliminates interconnect delays, reduces board space, and maintains full functional equivalence - making SN74F657DWRE4 a drop-in solution for designs originally using those two discrete ICs.

What package type and RoHS status does the SN74F657DWRE4 use?

The SN74F657DWRE4 uses a 24-pin SOIC (DW) package with 300-mil width, NiPdAu lead finish, and is RoHS-compliant (lead-free). It carries a moisture sensitivity level (MSL) rating of Level-1 (unlimited floor life at ≤30°C/60% RH), and is qualified for reflow up to 260°C peak temperature - consistent with standard JEDEC requirements for SN74F657DWRE4 manufacturing and assembly.